Superabsorbent foams based on crosslinked monomers comprising acid groups are known, cf. EP 858 478 B1, WO 97/31971 A1, WO 99/44648 A1 and WO 00/52087 A1. They are produced for example by foaming a polymerizable aqueous mixture comprising not less than 50 mol % neutralized acid-functional monoethylenically unsaturated monomers, crosslinkers and at least one surfactant and then polymerizing the foamed mixture. The foaming of the polymerizable mixture can be effected for example by dispersing fine bubbles of a gas which is inert toward free radicals or by dissolving such a gas in the polymerizable mixture under elevated pressure and depressurizing the mixture. The water content of the foams is set in the range from 1% to 60% by weight for example. The foams may be subjected to surface-postcrosslinking, if appropriate, by spraying a crosslinker onto the foamed material or dipping the foam into the crosslinker and heating the crosslinker-laden foam to a higher temperature. The foams are used for example in hygiene articles to acquire, distribute and store body fluids.
WO 03/066717 A2 discloses a process whereby wet strength is enhanced and residual monomer content lowered for superabsorbent foams by addition of amino-comprising polymers.
WO 2004/007598 A1 discloses water-absorbing foams comprising finely divided hydrophilic silicon dioxide and/or a surfactant at the surface. The treatment of the foams leads to an increase in the takeup rate for liquids.
WO 2004/035668 A2 discloses water-absorbing foams comprising superabsorbent fibers or fruit fibers, in particular apple fibers.
WO 2006/094977 A2 describes water-absorbing foams comprising wood fibers or waste paper fibers.
WO 2005/042 039 A2 describes hydrogels possessing enhanced blood absorbence due to their being coated with hydrophobic compounds.
The present invention has for its object to improve the properties of feminine hygiene absorbent articles comprising superabsorbent foams, in particular by providing foams that have good absorbing, retaining and conducting properties for aqueous fluids and are stable, in particular in the wet state, efficiently handlable, efficiently processible and simple to produce.
The present invention further has for its object to provide feminine hygiene absorbent articles comprising superabsorbent foams which swell one-dimensionally only and which do not shrink on drying.